Indigo paste.



UNITED STATES PATENT OFFICE.

PAUL SEIDEL, OF LUDWIGSHAFEN, GERMANY, ASSIGNOR TO BADISCHE ANILIN ANDSODA FABRIK, OF LUDWIGSI-IAFEN, GERMANY, A COR- PORATI ON.

INDIGO PASTE.

SPECIFICATION forming part of Letters Patent No. 692,720, dated February4, 1902.

Application filed June 15, 1900. Serial No. 20,433- (No specimens.)

To all whom, it may concern.-

Be it known that I, PAUL SEIDEL, doctor of philosophy, a subject of theKing of Saxony, residing at Ludwigshafen-on-the-Rhine, in the Kingdom ofBavaria, Germany, have invented new and useful Improvements in IndigoPaste, of which the following is a specification.

In the preparation of indigo in paste form for commercial purposes frompure indigo for example, synthetical or refined plant indigoit hashitherto proved difficult to obtain a concentrated paste containing,say, twenty to forty per cent. of indigo which is at the same timesufliciently liquid to be poured and does not deposit the indigo as aprecipitate. Especially troublesome in this respect is the tendency ofpure indigo to form a froth when being made into a paste with Water. Ihave found that this difficulty may be remedied and a nobile andnon-settling paste obtained by adding a very small quantity of athickening agent (protein or gummy substance) to the indigo which is tobe brought into the paste form. V For this purpose the followingsubstances are suitable: bone-glue, skin-glue, fish-glue, silk-gum,albumen casein, gluten, gelatin, gum solution, starch, dextrine, and thelike, and it is desirable that the indigo paste be neutral or alkaline.In this way concentrated pastes may be obtained which are suflicientlyliquid to be poured and do not deposit indigo.

The following examples serve to show how my invention may be carriedinto practical effect. The parts are by weight.

Example 1: Gradually add while well stirring one thousand (1,000) partsof indigo press-cake containing forty per cent. of indigo to a solutionof two (2) parts of gum in five hundred (500) parts of water. The massis soon resolved into an even thick paste which can be brought to theconsistency of twenty per cen 17., preferably used, by the further ad'-dition of five hundred (500) parts of water.

Example 2: Add a solution of one (1) part of gum in one thousand (1,000)parts of water to four hundred (400) parts of indigo-powder in asuitable grinding apparatus and there'- upon two parts of caustic-sodalye, (containing about fourteen per cent. of NaOH.) Set the apparatus inmotion. The indigo soon becomes moist and in a short time is ground upto an even paste, which can be diluted with water to any desiredstrength.

Now what I claim is- 1. As a new product the composition of mat PAULSEIDEL.

Witnesses:

ERNEST E. EHRHARDT, ALEXANDER ALLBRECI-IT.

